Method and apparatus for trimming and balancing vehicle wheels

ABSTRACT

A method and apparatus for trimming tires and balancing wheels which includes a fixed frame structure pivotally supporting thereon a wheel-support frame that carries a rotatable wheelmounting assembly, adapted to be selectively connected with an electric motor by a clutch; the wheel support frame includes a displaceable weight as well as a pointer to indicate any imbalance in the wheel when the clutch is disengaged and when a latch mechanism is unlatched to permit free pivotal movement of the wheel-support frame together with the wheel mounted thereon; the fixed frame structure also pivotally supports a trimming apparatus which can be manually pivoted and adjusted for removing any out-of-round conditions of the tread surface of the tire when the latter is rotated with the clutch engaged and the latch mechanism latched.

United States Patent [191 Branick Jan. 15, 1974 METHOD AND APPARATUS FORTRIMMING AND BALANCING VEHICLE WHEELS Inventor: Charles Earl Branick,1601 S. 9th

St., Fargo, N. Dak. 58102 [22] Filed: Dec. 7, 1970 [2]], Appl. No.:95,717

[52] [1.8. CI. 73/480 [51] Int. Cl. G0lm 1/12 [58] Field of Search73/459, 66, 460, 73/480 [56] References Cited UNITED STATES PATENTS2,146,417 2/1939 Catalano 73/459 2,322,939 6/1943 Inman 73/459 X2,334,991 1l/1943 Castiglia 73/459 X 3,581,576 6/1971 Reiser 73/459FOREIGN PATENTS OR APPLICATIONS 898,021 6/1962 Great Britain 73/459114,195 3/1918 Great Britain 73/459 Primary Examiner-James J. GillAttorney-Craig, Antonelli, Stewart & Hill [57] ABSTRACT A method andapparatus for trimming tires and balancing wheels which includes a fixedframe structure pivotally supporting thereon a wheel-support frame thatcarries a rotatable wheel-mounting assembly,

adapted to be selectively connected with an electric motor by a clutch;the wheel support frame includes a displaceable weight as well as apointer to indicate any imbalance in the wheel when the clutch isdisengaged and when a latch mechanism is unlatched to permit freepivotal movement of the wheel-support frame together with the wheelmounted thereon; the fixed frame structure also pivotally supports atrimming apparatus which can be manually pivoted and adjusted forremoving any out-of-round conditions of the tread surface of the tirewhen the latter is rotated with the clutch engaged and the latchmechanism latched.

11 Claims, 6 Drawing Figures PATENTED JAN 1 51974 SHEEY 1 OF 4 INVENTORATTORNEYS PAIENTEUJAN 1 s m SNtET 2 OF 4 INVENTOR I ATTORNEYS PATENIEDJAN 1 56974 SHEEI 8 ll? 4 INVENTOR FIG. 5

ATTORNEYS METHOD AND APPARATUS FOR TRIMMING AND BALANCING VEHICLE WHEELSThe present invention relates to amethod for trimmingand balancingwheels as well as to a combined tire-trimming and wheel-balancingmachine for motor vehicle wheels, and more particularly to such amachine as is able to perform the trimming of the tire as well as thestatic and dynamic balancing of the wheel with the tire mounted thereon.

The problem of eliminating imbalances in the wheels of motor vehicleshas been recognized for some time, and various apparatus for trimmingtires as well as various machines for statically and dynamicallybalancing the wheels have been proposed and, to some extent, have alsobeen commercially available. Trimming has been used to remove slightsurface portions of the tire along the tread surface thereof so as toeliminate outof-round conditions. However, the out-of-round condi tionsare not the only source of the problems of imbalances in wheels. As isknown, the wheels also must be balanced statically as well asdynamically.

With increasing speeds of presently available motor vehicles, theseproblems become ever more significant since even slight defects in thetire tread surface and/or slight imbalancesof the wheel can lead toserious difficulties in the handling of the vehicles. Additionally, theriding com-fort is greatly affected thereby.

Various machines have been proposed heretofore to solve these problems.However, these prior art machines involved principally two drawbacks;namely, (a) they were unableto perform with one and the same machine allthe necessary functions to eliminate any troubles from out-of-roundconditions of thetires and imbalances of the wheel, and (b) they wereall relatively complicated and costly in structure, particularly sincethey relied on high-speed rotaton of the wheel to achieve dynamicbalance, not to mention the need of skilled personnel to operate thesame.

A principal object of the present invention is to avoid theaforementioned shortcomings and drawbacks encountered in the prior art.

Another object of the present invention resides in a machine which issimple in construction yet capable of performing the functions oftire-trimming, static balancingand dynamic balancing.

A furtherobject of the present inventionresides in a combinedtire-trimming and wheel-balancing machine which obviates the need forhigh-speed rotation to achieve dynamic balancing, thereby considerablyreducing the cost.

Another object ofthe present inventionresides in a combinedtire-trimming and wheel-balancingmachine which greatly simplifies theprocedure to obtain a perfectly running tire to the point where it canbe carried out by relatively unskilledpersonnel.

Theseand further objects, features, and advantages of the presentinvention will become more obvious from the following description whentaken in connection with the accompanying drawing, which shows, forpurposesof illustration only, one embodiment in accordance with thepresent invention, and wherein:

FIG. 1 is a front elevation'al view of a combined tiretrimmingandwheel-balancing machine in accordance with the present invention;

FIG. 2 is a left side elevational view of the combined tire-trimming andwheel-balancing machine of FIG. 1;

FIG. 3 is a top plan view of the machine of FIG. 1;

FIG. 4 is a perspective view of only the wheel-support frame for themachine in accordance with the present invention;

FIG. 5 is a perspective view of the T-shaped weight used with themachine of the present invention; and

FIG. 6 is a partial cross-sectional view, on an enlarged scale, throughthe hub assembly of the wheel in accordance with the present invention.

The machine according to the present invention consists of a stationarybase provided with an upright support member carrying at its upper endan outwardly projecting fixed support structure on which is pivotallymounted the wheel-support frame; the wheel-support frame, in turn,carries a rotatably supported shaft on which is mounted the wheel hub.The rotatable shaft is adapted to be connected by way of a clutch with adriving motor so as to rotate the tire during trimming. Additionally, afixing means is provided to hold the wheel support frame fixedly, i.e.,non-pivotal relative to the stationary support structure during thetrimming operation, when the clutch is engaged. A displaceable weight isprovided at the wheel-support frame to balance the latter to its propervertical position with the tire mounted on the shaft. A trimmer, drivenby an electric motor and provided with the necessary feed and controlmechanisms for the cutting blade is mounted on'a trimmer frame,pivotally supported at the upright support member.

Themethod according to the present invention essentially consists inlatching the latching means to hold the wheel-support frame stationaryrelative to the fixed upright support, trimming the tire by means of thecutting blade on the pivotally mounted trimmer frame while rotating thewheel by the trimmer motor with the clutch engaged. Upon completion ofthe trimming operation, the trimmer motor is stopped, the clutch isdisengaged, and the latching means holding the pivotal wheel-supportframe fixed at the stationary frame is unlatched, whereupon the weightis adjusted to place the wheel support frame in a perfectly verticalposition; after completing the static balance by placing weights on therim in the usual manner, the wheel is then dynamically balanced byslowly rotating the same by hand and observing the deflections of apointer provided at thewheel support frame in relation to a fixed mark,and changing the balancing weights of the wheel to one or the otherside, as required, to achieve dynamic balanc mg.

Referring now more particularly to the drawing wherein like referencenumerals are used throughout the various views to designate like parts,the relatively fixed frame structure generallydesignated by referencenumeral 10 includes a conventional pedestal assembly generallydesignated by reference numeral 11 and consisting, for example, offourlegs 12 adjustable in height In a conventional manner, carrying baseplates 13 of any appropriate configuration. Caps 14 may be pro videdtocover the base plates 13 in order to increase its rigidity and improveits appearance. Suitably secured on this base assembly 11 is an uprightsupport column 16 of any suitable shape and configuration. Levels 17 and17' indicated only schematically and 10'; cated in any appropriate placeon the upright 16 to permit its installation in a perfectly verticalposition, are provided on the upright 16 to assist in setting up themachine in relation to the floor to assure that the up right support 16is perfectly vertical. The upright support 16 carries at its upper end afixedly secured mounting support generally designated by referencenumeral 20 which consists of two horizontal cross members 21 (FIG. 3)fixedly secured in any conventional manner at the upright 16; the crossmembers 21 are adjoined by substantially vertically extending members 22(FIGS. 1, 2 and 3) which in turn pass over into upwardly, outwardlyextending members 22' that in turn are interconnected by a cross member23 to form a substantially U-shaped frame as viewed in top plan view(FIG. 3). The cross member 23, in turn, is provided with a downwardlyextending bearing structure generally designated by reference numeral 24suitably secured thereto, for example, by welding. The bearing structure24 may be constituted, for example, by two spaced lug members 24'provided with bearing eyes or sockets to receive the pin-like endportions 41 (FIG. 4) of the pivot journal 41 of the wheel support framestructure generally designated by reference numeral 40. Any suitableconstruction may be used for the bearing journal structure 24, forexample, a split-type construction bolted together to facilitateassembly. Additionally, any suitable anti-friction bearingsschematically indicated only and designated by reference numeral 26 areprovided to facilitate the pivotal movement of the wheel support frame40 in the bearing eyes of the bearing structure 24. In actualconstruction for the sake of simplicity of manufacture and assembly,journal 40 may be hollow to support thereon shaft 161, the ends of whichare rotatably supported by bearings 26 in the bearing eyes of thebearing structure 24 and held in place by snap rings.

The wheel support frame 40 includes a pivot journal 41 forming thepin-like bearing ends 41. The wheelsupport frame 40 essentially consistsof two upper frame members 42, for example, of square cross section andsecured to similar vertical frame members 43 with a reinforcing spacermember 44 provided at the upper end of the frame members 43 to maintainthe frame members 42 and 43 at predetermined spacing from each otherwhile at the same time reinforcing the frame. The lower ends of theframe members 43 are connected with horizontal frame members 44 wherebyagain a reinforcing spacer member 45 is secured to assure the properspacing of the frame members 43, 43 and 44, 44. A tubular member 46(FIGS. 4 and 6) which projects through the space between upright framemembers 43 and is suitably secured thereto, serves by the use ofanti-friction bearings 47 and 48 as bearing journal for the drive shaft49 intended to rotate the hub of the wheel mounted thereon, as will bedescribed more fully hereinafter. The tubular member 46 is suitablysecured to the upright frame members 43, 43, for example, by welding,utilizing also, for example, triangularly shaped support brackets 50welded to the upright frame members 43 and to the tubular member 46. Ascan be seen from FIG. 4, the free ends of the lower frame members 44form therebetween a channel designated by reference numeral 51 toreceive therein the center leg 61 of a substantially T-shaped weightgenerally designated by reference numeral 60 which slides with itsbottom surfaces 63 of the cross leg 62 along the top surfaces 44' of theframe members 44.

A latching or locking mechanism generally designated by referencenumeral 70 (FIG. 2) consists of two similar tubular portions 71 and 72,which are fixedly mounted relative to the wheel-support frame 40 and thefixed frame structure 10, respectively, for example, by being secured toa frame member 43 and/or 44 and to an outwardly projecting arm 74suitably secured to the upright 16. The tubular portions 71 and 72 arethereby so mounted that they can be aligned in a given position of thepivotal wheel-support frame 40 so that latching pin 73, slidablyreceived within the tubular member 71, is able to latch together thewheel-support frame 40 and the fixed frame structure 10, 20 when the pin73 also extends through the aligned tubular member 72, whence thewheel-support frame 40 is unable to carry out any further pivotmovements. When so latched the axis of shaft 49 is coaxial t0 the driveshaft 101 of drive motor 100 and substantially at right angle tovertical axis of upright 16.

A shoulder 81 (FIG. 6) is suitably secured, for example, by welding orpress-fit on the shaft 49 and includes a plurality of uniformlydistributed pin-like members 82 secured thereto for engagement incomplementary apertures 84 provided in the adaptor ring 83. The adaptorring 83, in turn, is provided with a plurality of uniformlycircumferentially spaced mounting members generally designated byreference numeral 86 which consist of a base portion 86 secured bypress-fit in appropriate bores 83 provided in the adaptor ring 83, of anoutwardly projecting pin portion 86" to engage into the customary holesin the wheel hub and of a selfcentering portion 86 having asubstantially conically shaped configuration so as to automaticallycenter the wheel hub thereon. The outer end of the shaft 49 is providedwith an external thread 49 over which is screwed the handle generallydesignated by reference numeral 90. The adaptor ring 83 is also providedwith a plurality of circumferentially spaced hub-engaging membersgenerally designated by reference numerals 86a, which are similar to themembers 86 but project from the opposite side and are spaced at adifferent radial distance for use on wheels of different diameter. Itis, of course, understood that the hub assembly, i.e., the handle 90 aswell as the shoulder 81 and adaptor 83 with their respective parts, isproperly balanced in order to avoid any erroneous indications during thebalancing operatron.

Pointed markers 76 and 77 (FIG. 2) are provided at a frame member 44 andat the arm 74 in such a manner that the pointers coincide when thewheel-support frame 40 is in its true vertical position, assuming, ofcourse, also that the fixed frame structure 10, 20 is properly set up inits vertical position.

The electric motor with appropriate gear reduction box generallydesignated by reference numeral (FIG. 2) and of any conventionalconstruction includes the output shaft 101, adapted to be connected withthe shaft 49 by way of mutually complementary claw clutch elements 103and 104 of a claw clutch generally designated by reference numeral 102.While the shaft 49 is held axially immovable during operation, the shaft101 is adapted to be moved in its axial direction, schematicallyindicated by arrow 105 to provide engagement and disengagement of theclaw clutch 102. While a claw clutch is illustrated, it is understoodthat any other clutch may be used in its place or in the alternative, afriction wheel drive may be used. The engagement and disengagement ofthe claw clutch 102 may take place by conventional means, notillustrated. It is further understood that shaft 49 may be adjustedaxially by any conventional means to compensate for tires havingdifferent widths in order to center the tire for proper arcuation oftrimmer, i.e., to assure coincidence of the pivot axis of the trimmingapparatus with the center axis CC (FIG. 2) through the tire. This can beachieved in its simplest form by adjustably supporting tubular member 46to permit axial adjustment thereof within a further tubular support (notshown) secured to frame members 43 and brackets 50. Drive shaft 101 maybe provided in that case with conventional means enabling acorresponding axial adjustment. Of course, in the event of a frictionwheel drive, it is only necessary to make the driving or driven wheel ofsufficient width to compensate for relative axial movement between thetwo wheels. On the other hand shaft 49 could be so constructed andarranged as to slide through bearings 47 and 48 with conventional fixingmeans to hold shaft 49 in a given axial position.

The trimming apparatus generally designated by reference numeral 140 (FIG. 1) is also pivotally supported on the fixed frame structure 10.However, since the pivot axis for the trimming apparatus must coincidewith the vertical axis C--C passing through the center of the wheel, asuitable bracket member 18 or the like (FIG. 2) is fixedly secured inany appropriate manner to the upright support column 16 so as to projectoutwardly therefrom. The pivotal trimmer frame generally designated byreference numeral 120 (FIG. 1) for the timmer apparatus consists, forexample, of profile members 121 and 122 arranged in the form of an L andbraced by strut 123. The profile member 121 is secured at its lowerinner end to a pivot trunion 124 rotatably supported in bearing eyes 125and 126 which are suitably bolted or secured in any other manner to theplate 18. The pivot trunion 124 is provided with upwardly and downwardlyprojecting pin-like bearing shaft portions I24 and 124" rotatablysupported in corresponding bearing eyes by means of anti-frictionbearings 127 and 128 (FIG. 1).

Secured to the upper end of the upright trimmer framemember 122 is thetrimming apparatus, known as such, which includes a conventional feedmechanism 130 consisting of a hand wheel to adjust the cutting depth ofthe trimmer generally designated by reference numeral 140 that, in turn,includes a conventional cutter blade 141 rotated at the correct speed byan electric motor 142. The trimmer 140 is thereby suitably mounted byappropriate support means 143 on the movable part of the feed mechanism130 in a conventional. manner. Additionally, a U-shaped actuating handle129 is secured onto the upright trimmer frame member 122 to permitmanual pivoting of the trimmer during operation.

OPERATION In operation, when the machine in accordance with the presentinvention is initially installed, the legs 12 of the base are adjustedso that the upright 16 is vertical as determined by levels 17, 17'.Thereafter, the latch ing mechanism 70 is latched, a wheel to beadjusted is mounted on the hub assembly 80 by means of the handle 90 andthereafter the clutch 102 is engaged and the electric motor 100 isenergized by suitable actuation of its control provided in the switchbox 150. As the vehicle wheel now rotates on the shaft 49, driven by theelectric motor 100 by way of a gear reduction, for example, at a speedof 6 to rpm., the electric motor 142 is also turned on so as to rotatethe cutting blade 141. The trimmer mechanism is now used in aconventional manner by manually pivoting the trimmer frame 120 about thevertical pivot axis 160 and adjusting the feed mechanism 130 as requiredto remove any out-ofround condition of the tire tread surface.

After completion of this operation, the trimmer motor 142 as well as thedrive motor for the clutch shaft 101 are turned off and the clutch 102is disengaged. After that, the latching mechanism is unlatched so thatthe wheel support frame 40 together with the wheel mounted on the hubassembly are free to pivot about the horizontal pivot axis 161 (FIG. 1)formed by the bearing support 24, 41, 41 Next, the weight 60 is movedinwardly or outwardly within the groove 51, as required, until thepointers 76 and 77 are aligned. A level 56 may also be provided for thisadjustment which should be adjusted to a perfectly horizontal positionof the frame members 44, assuming a perfect right angle relationshipbetween the frame members 44, 43 and 42, respectively, the marker 77being disposed in a vertical plane containing the pivot axis 161 whilethe marker 76 is disposed in a plane parallel to the upright framemembers 43 and also containing the pivot axis 161. After the assembly isthus balanced, the wheel is initially statically balanced in aconventional manner by installing the usual counter-weights at the wheelrim. After the tire is balanced statically, the tire is then balanceddynamically by rotating the same slowly by hand while observingdeflections of the pointer 76 relative to the pointer 77, whereupon thebalancing weights are switched from one side of the wheel rim to theother until the tire remains in a perfectly straight line (plane) whenrevolved slowly, which is the case when the marker 76 remainssubstantially immovably in alignment with the marker 77.

After that, the handle is removed and the thusrounded and balanced wheelis removed for installation on the vehicle.

The particular arrangement of the pivotally mounted wheel-support frameon the fixed frame structure provides an extremely sensitive, yet verysimple means to indicate any dynamic imbalances even at slow speeds ofrotation of the wheel, when turned by hand. This is of great advantagenot only from a cost point of view but also from the point of view ofease of handling.

In order to handle wheels of all types and of all makes, various adaptorrings 83 may be provided which can be readily installed and interchangedin the construction of the present invention. Additionally, pinlikeprojections 86" greatly facilitate mounting of a wheel since the wheelwill be supported thereon while the handle 90 is tightened, therebyobviating the need for holding the wheel on the conical surfaces 86", asrequired in the prior art, during such tightening.

While I have shown and described only one embodiment in accordance withthe present invention, it is understood that the same is not limitedthereto but is susceptible of numerous changes and modifications asknown to those skilled in the art, For example, the frame and profilemembers may be of any suitable configurations and cross sections, whilethe pointers 76 and 77 as well as the various levels may also bearranged in different places. Furthermore, the various structural partsused in the machine according to the present invention may be of anyconventional type. Moreover, the fixed frame structure may also be ofany other equivalent construction, for example, may consist of anupright with outwardly extending arms or the like at the upper endthereof. Instead of a claw clutch, a friction clutch or other similardevice may be used. Thus, it is obvious that the present invention isnot limited to the details shown and described herein and I therefore donot wish to be limited to the same but intend to cover all such changesand modifications as are encompassed by the scope of the appendedclaims.

I claim:

1. A method of dynamically balancing a statically balanced wheel with atire mounted thereon, characterized in mounting the wheel on a rotatableshaft supported on a wheel-support frame, pivotally suspending saidwheel-support frame from a fixed frame structure, adjusting a weight onsaid wheel-support frame so that the wheel-support frame assumes apredetermined position relative to said fixed frame structure, slowlyrotating the wheel on said shaft and shafting balancing weights on therim of said tire from one side to the other side in accordance withdeflections of said wheelsupport frame from said predetermined position.

2. A method according to claim 1, characterized in that said wheel isfirst statically balanced after being mounted on said shaft by fixingbalancing weights to the rim thereof in accordance with the staticimbalance conditions of the wheel as mounted on said shaft.

3. A wheel balancing apparatus for the wheels of a motor vehicle whichhas tires on the wheels, comprising relatively fixed frame meansincluding upwardly and outwardly extending frame members, wheelsupportframe means pivotally suspended from said extending frame membersincluding rotatable support means for a vehicle wheel, pivotal bearingmeans for pivotally suspending said wheel-support frame means, saidpivotal bearing means being arranged at said upwardly and outwardlyextending frame members directly above said vehicle wheel and in a planeperpendicular to the axis of rotation of said wheel, adjusting means foradjusting said wheel-support frame means to a predetermined position,and indicating means for indicating said predetermined position, as wellas pivotal deflections therefrom.

4. An apparatus according to claim 3, characterized in that thewheel-support frame means includes two substantially parallel framemembers, held at a predetermined separation by spacer means, includingtwo upright frame portions with horizontal frame portions at the topthereof and horizontal frame portions at the bottom thereof, and atubular member secured to said upright frame portions.

5. An apparatus according to claim 4, characterized in that said tubularmember supports therein by antifriction bearings a rotatable shaftforming said rotatable support means, and said tubular member beingfixedly secured to said upright frame portions by reinforcing platemeans.

6. An apparatus according to claim 5, characterized in that saidrotatable shaft is adjustable in its axial direction relative to thewheel-support frame means to compensate for different tireconstructions.

7. An apparatus according to claim 4, characterized in that said bottomhorizontal frame portions are separated by said spacer means toeffectively form an aperture for slidingly receiving an adjustableweight forming said adjusting means.

8. An apparatus according to claim 7, characterized in that said weightis of substantially T-shape with its center leg extending into theaperture and sliding with its cross-arm on the top surfaces of saidbottom horizontal frame portions of the wheel support frame means.

9. An apparatus according to claim 3, characterized in that said wheelsupport frame means is pivotally suspended from said pivotal bearingmeans above the axis of the rotatable wheel support means by a distancegreater than one half the diameter of a tire mounted on the largest sizewheel to be accommodated, and in that said indicating means is locatedbelow said axis by at least about one half said wheel diameter.

10. An apparatus according to claim 3, characterized in that said planeis the center plane disposed in the circular cross-section of the wheel.

11. An apparatus according to claim 10, characterized in that saidindicating means is disposed below the wheel in the center plane of thewheel.

1. A method of dynamically balancing a statically balanced wheel with atire mounted thereon, characterized in mounting the wheel on a rotatableshaft supported on a wheel-support frame, pivotally suspending saidwheel-support frame from a fixed frame structure, adjusting a weight onsaid wheel-support frame so that the wheel-support frame assumes apredetermined position relative to said fixed frame structure, slowlyrotating the wheel on said shaft and shafting balancing weights on therim of said tire from one side to the other side in accordance withdeflections of said wheel-support frame from said predeterminedposition.
 2. A method according to claim 1, characterized in that saidwheel is first statically balanced after being mounted on said shaft byfixing balancing weights to the rim thereof in accordance with thestatic imbalance conditions of the wheel as mounted on said shaft.
 3. Awheel balancing apparatus for the wheels of a motor vehicle which hastires on the wheels, comprising relatively fixed frame means includingupwardly and outwardly extending frame members, wheel-support framemeans pivotally suspended from said extending frame members includingrotatable support means for a vehicle wheel, pivotal bearing means forpivotally suspending said wheel-support frame means, said pivOtalbearing means being arranged at said upwardly and outwardly extendingframe members directly above said vehicle wheel and in a planeperpendicular to the axis of rotation of said wheel, adjusting means foradjusting said wheel-support frame means to a predetermined position,and indicating means for indicating said predetermined position, as wellas pivotal deflections therefrom.
 4. An apparatus according to claim 3,characterized in that the wheel-support frame means includes twosubstantially parallel frame members, held at a predetermined separationby spacer means, including two upright frame portions with horizontalframe portions at the top thereof and horizontal frame portions at thebottom thereof, and a tubular member secured to said upright frameportions.
 5. An apparatus according to claim 4, characterized in thatsaid tubular member supports therein by anti-friction bearings arotatable shaft forming said rotatable support means, and said tubularmember being fixedly secured to said upright frame portions byreinforcing plate means.
 6. An apparatus according to claim 5,characterized in that said rotatable shaft is adjustable in its axialdirection relative to the wheel-support frame means to compensate fordifferent tire constructions.
 7. An apparatus according to claim 4,characterized in that said bottom horizontal frame portions areseparated by said spacer means to effectively form an aperture forslidingly receiving an adjustable weight forming said adjusting means.8. An apparatus according to claim 7, characterized in that said weightis of substantially T-shape with its center leg extending into theaperture and sliding with its cross-arm on the top surfaces of saidbottom horizontal frame portions of the wheel support frame means.
 9. Anapparatus according to claim 3, characterized in that said wheel supportframe means is pivotally suspended from said pivotal bearing means abovethe axis of the rotatable wheel support means by a distance greater thanone half the diameter of a tire mounted on the largest size wheel to beaccommodated, and in that said indicating means is located below saidaxis by at least about one half said wheel diameter.
 10. An apparatusaccording to claim 3, characterized in that said plane is the centerplane disposed in the circular cross-section of the wheel.
 11. Anapparatus according to claim 10, characterized in that said indicatingmeans is disposed below the wheel in the center plane of the wheel.